In recent years, technologies relating to IP-based mobile networks have been used in the telecommunications network. As an example, IP-based Radio Access Network (RAN) (abbreviated as IP RAN) has been introduced, IP RAN is a resolution which combines Layer-2 and Layer-3 Virtual Private Network (VPN) technologies based on Multi-Protocol Label Switching (MPLS) protocol. Layer-2 Virtual Private Network (L2VPN) and Layer-3 Virtual Private Network (L3VPN) respectively provide a private network service among a set of customer sites using a service provider's existing MPLS and IP network. In a Layer-2 VPN, the Layer-3 routing of customer traffic occurs within the customer's network. In a Layer-3 VPN, the Layer-3 routing of customer traffic occurs within the service provider's network. The IP RAN technology satisfies requirements for backhaul communication from base stations. In IP RAN networking, layer-2 access networks may be isolated from one another by L2VPN. And access network routing and core network routing may be isolated by L3VPN. A network device, which is located at the intersection between an access network and a core network, may connect a layer-2 access network and a layer-3 core network by mutual accessing between L2VPN and L3VPN. In the downlink direction from L3VPN to L2VPN, the rate on the network device for forwarding packets from L3VPN to L2VPN may influence the performance of IP RAN.